1. Field of the Invention
This invention relates to a jaw clutch, and more particularly to a jaw clutch coupling mechanism suitable for use on working vehicles such as power rice-planters, power cultivators, ultra mini shovel cars and the like, having steel ball drop-in portions with a broadened contact surface to ensure improved surface pressure strength, and to a shift lever link mechanism adapted to reduce the shocks of engagement at the time of operating a shift lever.
2. Description of the Prior Art
FIGS. 11 through 14 illustrate a conventional jaw clutch of this sort. Shown in FIG. 11 is a jaw clutch for switching the operation either to forward or reverse drive, wherein indicated at 1 and 2 are forward and reverse gears which are provided with opposingly disposed cylindrical extensions 3 and 4, respectively, and which are rotatable in opposite directions about a driven shaft 5. The extensions 3 and 4 are provided with open holes 6 in uniformly spaced positions in the circumferential direction to retain steel balls 7 therein. On the other hand, as shown in FIG. 12, the driven shaft 5 is provided with spline grooves 8 circumferentially at uniform intervals to provide ball drop-in portions in a pitch corresponding to the ball retainer holes 6. The spline grooves or drop-in portions 8 are formed in such a way as to have a width greater than the steel balls 7, providing a play to ensure that the steel balls 7 easily engage the drop-in portions 8.
Upon axially sliding a slider 9 which is fitted around the driven shaft 5 and gear extensions 3 and 4 by means of a shifter 10, the steel balls 7 of either the forward gear 1 or reverse gear 2 are pushed into the drop-in portions 8 on the driven gear 5 as indicated in phantom to transmit forward or reverse rotation to the driven gear 5.
Further, as shown in FIG. 13, the driven shaft 11 is provided with a plural number of rows of coupling grooves 12 on its circumferential surface in positions opposing the ball retainer holes 6. The drop-in portions 12 are in the form of slots extending in the circumferential direction and, as shown also in FIG. 14, have the respective opposite end portions 12a rounded in conformity with the shape of the steel balls 7.
The slider of the above-described jaw clutch is coupled with the shifter which is linked to a shift lever through a link mechanism for on-off operations of the clutch. However, there has been a problem that, when the shift lever is operated to engage the jaw clutch, the coupling members are repulsed by the shocks of engagement, and the coupling shocks are transmitted to the shift lever through the link mechanism and to the hand of the operator.
In the conventional jaw clutch shown in FIGS. 11 and 12, the ball drop-in portions 8 are provided with a play to facilitate the engagement of the steel balls 7. However, in case the drop-in portions 8 have a large play, the steel balls 7 are violently hit against the side walls 8a of the drop-in portions 8. Since, the ball drop-in portions 8a are in the form of spline grooves with straight side walls 8a in the axial direction, the steel balls 7 are brought into point contact with the side walls 8a, leaving percussive impressions d on the side walls 8a when the strength of the latter is deficient.
On the other hand, the steel balls 7 are easily engageable in case of the driven shaft 11 which is provided with drop-in portions 12 in the form of slots with rounded ends 12a as shown in FIGS. 13 and 14, but the process of machining the ball drop-in portions 12 by an end mill is time-consuming and leads to a higher production cost.